A regnal name, or reign name, is a name used by some monarchs and popes during their reigns. The term is simply the adjective "regnal", of or relating to a reign, monarch, or kingdom, modifying name.[1]

Since ancient times, monarchs have frequently, but not always, chosen to use a name different from their own usual personal name when they inherit a throne.

In some countries in Asia, monarchs took or take era names. While era names as such are not used in many monarchies, sometimes periods of time are named after a monarch (usually long-lived), or a succession of monarchs of the same name. This is customary; there is no formal or general rule. The whole period during which a succession of four Georges (George I, II, III, and IV) of the Hanoverian dynasty ruled became known as the Georgian era; although there were many Edwards, the Edwardian era always refers to the reign of Edward VII at the beginning of the 20th century.

Ancient rulers in many parts of the world took regnal names or throne names which were different from their personal name. This is known to be true, for instance, of several kings of Assyria, and appears to be the case for several Kings of Judah. In Ancient Egypt, Pharaohs took a number of names - the praenomen being the most commonly used, on occasion in conjunction with their personal name.

During the Medieval Age, when the House of Árpád disappeared in 1301, two of the monarchs that claimed the throne and were crowned chose a different name. Otto III, Duke of Bavaria became Bela V of Hungary, taking the name of his maternal grandfather, Béla IV of Hungary. In the other hand, Wenceslaus III of Bohemia signed his royal documents in Hungary as Ladislas, this being a very traditional name in the Kingdom.

Later during the first half of the 14th century, Charles I of Hungary signed as "Carolus rex", but in fact his birth name was the Italian Caroberto. This is why he is often referred to by the Hungarian historians as "Charles Robert of Hungary".

Though most monarchs of the United Kingdom have used their first baptismal name as their regnal name, on three occasions monarchs have varied from this trend; in the first of these, Queen Victoria had been christened Alexandrina Victoria, but took the throne under the name Victoria.

When Victoria's son, Prince Albert Edward, Prince of Wales, became king in 1901, he took the regnal name Edward VII, against the wish of his late mother.[citation needed] The new king declared that he chose the name Edward alone as an honoured name borne by six of his predecessors, and that he did not wish to diminish the status of his father, with whom alone among royalty the name Albert should be associated.

In 1936, after the abdication crisis, Prince Albert, Duke of York, assumed the throne as King George VI instead of using the King Albert. His full name was Albert Frederick Arthur George; like Edward VII and Victoria he used another of his names.

There has been speculation that the current heir-apparent to the British throne, Charles, Prince of Wales, may not elect to be known as "Charles III" out of concerns of comparison with Charles II of England (known as a playboy) and the Jacobite memory of the "Young Pretender" Charles Edward Stuart (who claimed the title "Charles III").[3] He may instead choose to be known as George VII in honour of his grandfather.[3] However, the Prince has not as yet publicly made any decision.[4]

When John, Earl of Carrick ascended the Scottish throne in 1390, it was deemed imprudent for him to take the regnal name of "John II", as recent kings named John had turned out badly in England as well as in Scotland. Furthermore, royal propaganda of the time held that John Balliol had not been a legitimate king of Scotland, making the new king's regnal number also a tricky issue. To avoid these problems, John took the regnal name of Robert III, honouring his father and great-grandfather.[5]

Upon the accession, in 1952, of Elizabeth II the title Elizabeth II caused controversy in Scotland as there had never been a Scottish Elizabeth I. The Prime Minister Winston Churchill informed the British House of Commons that the practice since the Union was to use the higher numeral. New Royal Mail post boxes in Scotland, bearing the cypherEIIR, were vandalised, after which, to avoid further problems, post boxes and Royal Mail vehicles in Scotland bore only the Crown of Scotland. A legal case, MacCormick v. Lord Advocate (1953 SC 396), contested the right of the Queen to title herself Elizabeth II in Scotland, arguing that to do so would be a breach of the Act of Union. The case, however, was lost on the grounds that the pursuers had no title to sue the Crown, and also that the numbering of monarchs was part of the royal prerogative, and thus not governed by the Act of Union.

All ruling male members of the House of Orange-Nassau bore the name Willem (William). The current king of the Netherlands was christened Willem-Alexander. During an interview in 1997 he said he intended to rule under the name of Willem IV, but he had a change of mind. In a televised interview just before his inauguration, he announced he would continue to use the name Willem-Alexander, saying "I spent 46 years of my life under the name Willem-Alexander, and specifically under the nickname of Alexander. I think it would be weird to discard that because I become king of the country." Furthermore, he said he did not consider himself "a mere number", adding that regnal numbers reminded him of Dutch cattle naming conventions.[6]

In the Ethiopian Empire, especially during the Solomonic dynasty, many Emperors would take a throne name, though this was not a general practice; a great number of rulers would remain known during their reign by their birth names. Yekuno Amlak, the founder of the Solomonic dynasty, took his father's name, Tasfa Iyasus, as his throne name. Yagbe'u Seyon, his son and heir, took the throne name Salomon after the biblical figure. Amda Seyon took the throne name Gebre Mesqel, "slave of the cross"; Tewodros I was Walda Ambasa, "son of the lion"; Sarwe Iyasus was Mehreka Nañ "distributor of your [the Lord's] mercy"; etc. Tafari Makonnen, the last sovereign Emperor of Ethiopia, took as his throne name Haile Selassie, meaning "Power of the Trinity".

In the various extant traditional states of the West African nation of Nigeria, the regnal names of the titled monarchs, who are known locally as the traditional rulers, serve two very important functions within the monarchical system. Firstly, seeing as how most states are organised in such a way as to mean that all of the legitimate descendants of the first man or woman to arrive at the site of any given community are considered its dynastic heirs, their thrones are usually rotated amongst almost endless pools of contending cousins who all share the names of the founders of their houses as primary surnames. In order to tell them all apart from one another, secondary surnames are also used for the septs of each of the royal families that are eligible for the aforementioned rotations, names that often come from the names of state of the first members of their immediate lineages to rule in their lands. Whenever any of their direct heirs ascend the thrones, they often use their septs' names as reign names as well, using the appropriate ordinals to differentiate themselves from the founders of the said septs. An example of this is found in the kingdom of Lagos, where the Adeniji-Adele family is distinguished from their numerous Adele cousins by the word Adeniji, which was actually the first name of the reigning founder of their branch of the dynasty, the Oba Adeniji Adele II. This distinction notwithstanding, both groups of dynasts (as well as a number of other ones that don't have the name Adele as an official surname, such as that of the Oloye Adekunle Ojora, a prominent nobleman of royal descent) are part of what is known as the Adele Ajosun Ruling House of Lagos.

Beyond that which is described above, regnal names also serve in Nigeria and indeed in much of Africa as chronological markers in much the same way that those of Europe do (e.g. the Victorian era). Whenever one hears of a person describing what happened at the time when so and so ruled over any particular place or people, what he or she is actually saying is that an event happened within a finite period of time, one that is equal to the duration of the reign of the monarch in question. Now seeing as how it is possible (and in fact common, particularly among the southern tribes) for one individual to have several different names and aliases in a single life, a certain degree of uniformity in usage is required if the history of an entire state is to be tied to his or her name. It is for this reason that when new monarchs are enthroned, the uniqueness of their names is usually considered to be a matter of considerable importance (even when it is caused by nothing more than the adding of ordinals to them or the allowing of more than a generation to pass before their subsequent usage). An example of this can be found in the kingdom of Benin, where the throne name of Erediauwa I has become the surname of all of his immediate family in the Eweka royal house of the state, thus nominally tying them and their descendants to the era of his reign. This is especially obvious when the reigning branch's name is compared to the last names of the king's brothers and their heirs, named the Akenzuas after his father Akenzua II, and his uncles and their heirs, named the Ewekas after his grandfather Eweka II.

In the case of the comparatively small number of Nigerian monarchs, such as Obi Nnaemeka Achebe of Onitsha, who do not make use of regnal names as a result of a variety of reasons, pre-coronation names are maintained during their reigns.

Immediately after a new pope is elected, and accepts the election, he is asked by the Dean of the College of Cardinals, "By what name shall you be called?" The new pope chooses the name by which he will be known. The senior Cardinal Deacon, or Cardinal Protodeacon, then appears on the balcony of Saint Peter's Basilica to proclaim the new Pope, informing the world of the man elected Pope, and under which name he would be known during his reign.

I announce to you a great joy:
We have a Pope,
The Most Eminent and Most Reverend Lord,
Lord [forename],
Cardinal of the Holy Roman Church [surname],
who conferred upon himself the name [papal name].

During the first centuries of the church, priests elected bishop of Rome continued to use their baptismal names after their elections. The custom of choosing a new name began in AD 533 with the election of Mercurius. Mercurius had been named after the Roman god Mercury, and decided that it would not be appropriate for a pope to be named after a Roman god. Mercurius subsequently decreed that he would be known as John II. Since the end of the tenth century the pope has customarily chosen a new name for himself during his Pontificate; however, until the 16th century some pontiffs used their baptismal names.

The last pope to use his baptismal name was Pope Marcellus II in 1555, a choice that was even then quite exceptional. The names chosen by popes are not based on any system other than general honorifics. They have been based on immediate predecessors, mentors, political similarity, or even after family members—as was the case with Pope John XXIII. The practice of using the baptismal name as papal name has not been ruled out and future popes could elect to continue using their original names after being elected pope.

Often the new pontiff's choice of name upon being elected to the papacy is seen as a signal to the world of whom the new pope will emulate or what policies he will seek to enact. Such is the case with Benedict XVI who, in fact, explained the reasons for his choice of name during his first General Audience in St. Peter's Square, on 27 April 2005. On that occasion, he said that he wanted to remember "Pope Benedict XV, that courageous prophet of peace, who guided the Church through turbulent times of war," and also "Saint Benedict of Nursia, co-patron of Europe, whose life evokes the Christian roots of Europe."

There has never been a Pope Peter II. Even though there is no specific prohibition against choosing the name Peter, bishops elected to the Papacy have refrained from doing so even if their own given name was Peter. This is because of a tradition that only Saint Peter should have that honor. In the 10th century John XIV used the regnal name John because his given name was Peter. While some antipopes did take the name Peter II, their claims are not recognized by the mainstream Roman Catholic Church, and each of these men only either has or had a minuscule following that recognized their claims.

Probably because of the controversial Antipope John XXIII, new popes avoided taking the regnal name John for over 600 years until the election of the other John XXIII. Immediately after John's election as Pope in 1958, there was some confusion as to whether he would be known as John XXIII or John XXIV, which he moved to immediately resolve by declaring that he would be known as John XXIII.

In 1978, Albino Luciani became the first pope to use two names for his regnal name when he took the name John Paul I, including the "I". He took the "John Paul" name to honor both John XXIII and Paul VI. With the unexpected death of John Paul I a little over a month later, Karol Wojtyła took the name John Paul II to honor his immediate predecessor.

Antipopes also have regnal names, and also use the ordinal to show their position in the line of previous pontiffs with their names. For example, David Bawden took the name Michael I when declared pope in 1990.